# What is a cross spectral matrix?

## What is a cross spectral matrix?

Many post-processing beamforming algorithms rely on the Cross Spectral Matrix (CSM) or, more accurately, the cross power spectral density matrix. The cross power spectral density, analogue to a time domain cross-correlation, is used in signal processing to estimate the degree of correlation between two signals.

## What is cross spectral density?

The cross spectral density (CSD) is one of several advanced graph functions used to compare signals. Specifically, it displays the distribution of power for a pair of signals across a frequency spectrum at any time. This information can be used to determine the influence of a signal in relation to another.

How do you calculate cross spectral density?

pxy = cpsd( x , y ) estimates the cross power spectral density (CPSD) of two discrete-time signals, x and y , using Welch’s averaged, modified periodogram method of spectral estimation. If x and y are both vectors, they must have the same length.

### What is spectral density matrix?

Spectral density matrix estimation of multivariate time series is a classical problem in time series and signal processing. In modern neuroscience, spectral density based metrics are commonly used for analyzing functional connectivity among brain regions.

### How do you calculate coherence?

The coherence calculation involves summing vectors to produce a dominant direction (determined by the coherence phase) and amplitude determined by the degree of coherence. Here the true coherence = 0> and = 8 random vectors are being summed. That they would sum to a zero-length vector is very improbable.

What is coherent frequency?

In physics, two wave sources are coherent if their frequency and waveform are identical. Coherence is an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference. Two waves are said to be coherent if they have a constant relative phase. 